This invention is directed to a surfactant comprising a heterocyclic group. More particularly, the invention is directed to a surfactant comprising a heterocyclic group that results in superior cleaning properties in a dry cleaning system.
In many cleaning applications, it is desirable to remove contaminants (e.g., stains) from substrates, like metal, ceramic, polymeric, composite, glass and textile comprising substrates. Particularly, it is highly desirable to remove contaminants from clothing whereby such contaminants include dirt, salts, food stains, oils, greases and the like.
Typically, dry-cleaning systems use organic solvents, like chlorofluorocarbons, perchloroethylene and branched hydrocarbons to remove contaminants from substrates. In response to environmental concerns, other dry-cleaning systems have been developed that use inorganic solvents, such as densified carbon dioxide, to remove contaminants from substrates. The systems that use carbon dioxide to remove contaminants from substrates generally employ a surfactant and a polar co-solvent so that a reverse micelle may be formed to trap the contaminant targeted for removal.
In view of the environmental concerns associated with dry cleaning in, for example, halogenated hydrocarbons, many cleaning establishments have expressed their interests in cleaning with continuous phase solvents that comprise densified gases such as densified carbon dioxide as well as a biodegradable functionalized hydrocarbon or a silicon comprising surfactant. Unfortunately, however, cleaning with such solvents is not made easy because only very few surfactants are compatible with such continuous phases.
It is of increasing interest to develop surfactants that enhance cleaning in a system that uses a densified gas, functionalized biodegradable hydrocarbon and/or a silicon comprising solvent. This invention, therefore, is directed to a surfactant comprising a heterocyclic group that unexpectedly results in superior cleaning properties in a dry cleaning system that utilizes a densified gas, a functionalized biodegradable hydrocarbon and/or silicon comprising solvent.
Efforts have been disclosed for dry cleaning with carbon dioxide. In U.S. Pat. No. 5,676,705, a superior dry cleaning method which employs densified carbon dioxide is described.
Other efforts have been disclosed for dry cleaning with carbon dioxide. In U.S. Pat. No. 5,683,473, a superior method for dry cleaning fabrics with a surfactant having a polysiloxane, branched polyalkylene oxide or halocarbon group is described.
Still further, U.S. Pat. No. 5,683,977 discloses a superior dry cleaning system with carbon dioxide and a surfactant adjunct.
Finally, in U.S. Pat. No. 5,866,005, a cleaning process using carbon dioxide as a solvent along with molecularly engineered surfactants is described.
In a first embodiment, the present invention is directed to a dry cleaning system comprising a surfactant having the formula:
Axe2x88x92Z
wherein A is a portion of the surfactant that is soluble in carbon dioxide and Z is a portion of the surfactant that is not soluble in carbon dioxide and Z comprises a heterocyclic group, with the provisos that:
(i) when Z is pyrrolidone, nitrogen is not substituted with a hydrocarbon having less than five carbon atoms;
(ii) when Z is a polymeric vinyl pyrrolidone, the dry cleaning system is a system for removing soil from fabrics;
(iii) when A is a polysiloxane, Z is not a beta carboxylic acid substituted pyrrolidone having the polysiloxane joined to nitrogen with a bridging radical; and
(iv) when A is not a hydrocarbon, Z is not a carbohydrate.
In a second embodiment, the present invention is directed to a method for dry cleaning using the dry cleaning system of the first embodiment.
There generally is no limitation with respect to the surfactant used in this invention as long as the surfactant will enhance cleaning in a system which utilizes a continuous phase solvent comprising a densified gas, biodegradable functionalized hydrocarbon or a silicon comprising solvent, and the surfactant meets the criteria set forth in the above-described provisos (i)-(iv).
Often, the surfactants which may be used in this invention are selected from the group consisting of 
wherein each R and T are independently a hydrogen, C5 to C18 hydrocarbon, polysiloxane, CO2 soluble polyalkylene oxide or halocarbon, with the proviso that at least T or one R group is not hydrogen, L is C(R2) or y-(T)t, x is an integer from about 1 to about 6, each y is independently N, P, S, B or 0 and t is 0 or 1 with the proviso that t is 0 when y is oxygen.
In a preferred embodiment the hydrocarbon is a C6 to C12 hydrocarbon, the polysiloxane is polydimethysiloxane with or without polypropylene oxide substituents and having a weight average molecular weight of about 200 to about 200,000, the polyalkylene oxide is polypropylene oxide having a weight average molecular weight of about 100 to about 100,000, and the halocarbon is a C2 to C8 fluoroalkylene or fluoroalkenylene, x is an integer from about 2 to about 4 and the heteroatom is N. The preferred polysiloxanes and halocarbons are derived from those described in U.S. Pat. Nos. 5,676,705, 5,683,473 and 5,683,977, the disclosures of which are incorporated herein by reference. The preferred polysiloxanes are often bridged to the heterocyclic group with a C1 to C20 hydrocarbon bridging radical, and preferably, a C3 hydrocarbon bridging radical.
In a most preferred embodiment, structure I represents the surfactant comprising a heterocyclic group and each R is hydrogen, y is N, T is a C8 or C12 hydrocarbon, L is C(R2), x is 2 and t is 1. When T is a C8 hydrocarbon, such a surfactant is sold under the name Surfadone LP-100 and when T is a C12 hydrocarbon, such a surfactant is sold under the name Surfadone LP-300, both of which are made commercially available by International Specialty Products. Still another most preferred embodiment results when at least one R is a C5 to C18 group, L is oxygen, y is oxygen and x is 2.
The surfactant comprising the heterocyclic group which may be used in this invention can be prepared via numerous well known processes which include the condensation of butyrolactone with methylamine. Such reactions are disclosed in The Kirk-Othmer Encyclopedia of Chemical Technology, Volume 20, 4th Edition, pages 697-720 (1996), the disclosure of which is incorporated herein by reference.
Other surfactants comprising heterocyclic groups which may be used in this invention (as defined by the formulas above) include those made and described in Introduction to Organic chemistry, Second Edition, Streitwieser, Jr. et al., Chapter 32 (1981), the disclosure of which is incorporated herein by reference.
Still other surfactants that may be used in this invention (as defined by the formulas above) include those prepared by a conventional hydrosilation reaction wherein at least one reactant comprises a heterocyclic group.
If desired, the surfactants which can be employed in this invention may be purchased from suppliers such as BASF, Arco and, again, International Specialty Products.
There generally is no limitation with respect to the continuous phase solvent (i.e., fluid) which may be employed with the surfactants comprising a heterocyclic group of this invention other than that the solvent is a densified gas (e.g., fluid which is a gas at standard temperature and pressure), a biodegradable hydrocarbon or a silicon comprising solvent, and capable of being a continuous phase in a dry cleaning application. Illustrative examples of the types of solvents which may be employed in this invention include a C2-C4 substituted or unsubstituted alkane, carbon dioxide, silicone oil, and an azeotropic solvent.
Regarding the solvent which is a densified gas, such a solvent may be, within the dry cleaning composition or process, a gas, liquid or supercritical fluid depending upon how densified the solvent is (how much pressure is applied at a given temperature) in the domestic or commercial cleaning application the solvent is used in. Propane and carbon dioxide tend to be the preferred solvents when the solvent selected is one which is a densified gas. Carbon dioxide, however, is especially preferred.
As to the silicon comprising solvent which may be used in this invention, such a solvent is typically a commercially available cyclic-siloxane based solvent made available from GreenEarth Cleaning, LLC. Such a solvent is generally one which has a flash point over about 65xc2x0 C., with octamethyl-cyclotetrasiloxane and decamethyl-cyclopentasiloxane being most preferred. A more detailed description of such conventional siloxane comprising solvents may be found in U.S. Pat. No. 5,942,007, the disclosure of which is incorporated herein by reference.
Especially preferred silicon comprising solvents are those having the formula: 
wherein each R is independently a substituted or unsubstituted linear, branched or cyclic C1-10 alkyl, C1-10 alkoxy, substituted or unsubstituted aryl, aryloxy, trihaloalkyl, cyanoalkyl or vinyl group, and R1 is a hydrogen or a siloxyl group having the formula:
Si(R2)3xe2x80x83xe2x80x83V
and each R2 is independently a linear, branched or cyclic C1-10 substituted or unsubstituted alkyl, C1-10 alkoxy, substituted or unsubstituted aryl, trihaloalkyl, cyanoalkyl, vinyl group, amino, amido, ureido or oximo group, and R1* is an unsubstituted or substituted linear, branched or cyclic C1-10 alkyl or hydroxy, or OSi(R2)3 whereby R2 is as previously defined, and e is an integer from about 0 to about 20.
The most preferred linear siloxane solvent is one wherein each R is methyl, R1 is Si (R2)3, R2 is methyl and R1* is methyl. Preferably, e is an integer from about 0 to about 10, and most preferably, an integer from about 2 to about 5.
Such solvents are made commercially available by General Electric, and Dow Corning under the name Dow Corning 200(R) fluid. A description of the solvents may be found in U.S. Pat. Nos. 3,931,047 and 5,410,007, the disclosures of which are incorporated herein by reference.
The biodegradable functionalized hydrocarbon that may be used in this invention includes those generally classified as an azeotropic solvent. Such an azeotropic solvent often comprises alkylene glycol alkyl ethers, like propylene glycol tertiary-butyl ether, and is described in U.S. Pat. No. 5,888,250, the disclosure of which is incorporated herein by reference. Moreover, as used herein, biodegradable functionalized hydrocarbon is defined to mean a biodegradable hydrocarbon comprising at least one member selected from the group consisting of an aldehyde, ketone, alcohol, alkoxy, ester, ether, amine, amide and sulfur comprising group.
When dry cleaning, for example, fabrics, like clothing or garments, with a solvent that is a densified gas (and the surfactants of this invention), the machine which is employed for cleaning is well known in the art. Such a machine typically comprises a gas supply, cleaning tank and condenser. The machine may further comprise a means for agitation. The means for agitation may be, for example, a mechanical device like a mechanical tumbler, or a gas-jet agitator. The art recognized machines which may be used in this invention (e.g., when a densified gas is used) may be found in U.S. Pat. Nos. 6,012,307, 5,943,721, 5,925,192, 5,904,737, 5,412,958, 5,267,455 and 4,012,194, the disclosures of which are incorporated herein by reference.
When dry cleaning for example, fabrics, like clothing or garments, with the biodegradable functionalized hydrocarbons or silicon comprising solvents and the surfactants described in this invention, the type of machine that may be used for the dry cleaning process is the same or substantially the same as the commonly used dry cleaning machines used for dry cleaning with perchloroethylene. Such machines typically comprise a solvent tank or feed, a cleaning tank, distillation tanks, a filter and solvent exit. These commonly used machines are described, for example, in U.S. Pat. No. 4,712,392, the disclosure of which is incorporated herein by reference.
When the fabric is placed in the machine and the continuous phase solvent of choice is fed into the machine, the normal cleaning cycle is run (typically between ten (10) minutes and one (1) hour). Prior to or after the start of the cleaning cycle, the heterocyclic surfactant of this invention is introduced into the cleaning machine. Any of the surfactants represented by formulae I to III may be used, including any combination thereof. Often, the amount of surfactant employed is from about 0.001 to about 15.0%, and preferably, from about 0.01 to about 5.0%, and most preferably, from about 0.01 to about 3.0% by weight of surfactant, based on total weight of surfactant and continuous phase solvent, including all ranges subsumed therein.
In addition to continuous phase solvent and the surfactant described in this invention, it is especially preferred to add from about 0.01% to about 10.0%, and preferably, from about 0.03 to about 3.0%, and most preferably, from about 0.05 to about 0.3% by weight of a polar additive (e.g., C1-10 alcohol and preferably water) based on total weight of continuous phase solvent, surfactant and polar additive, including all ranges subsumed therein. The addition of polar additive to the continuous phase solvent and surfactant is often desired so that cleaning may be enhanced, for example, by the formation of reverse micelles.
When cleaning fabrics, for example, with the surfactants of this invention, the pressure and temperature of the dry cleaning system (e.g., the system comprising the fabric targeted for cleaning, the continuous phase solvent and the surfactant described in this invention) within the machine is limited only to the extent that the temperature and pressure allow for the fabric to be cleaned. The pressure is often from about 14.7 to about 10,000 psi, and preferably, from about 200 to about 5,000 psi, and most preferably, from about 250 to about 3,000 psi, including all ranges subsumed therein. The temperature is often from about xe2x88x9230.0 to about 100xc2x0 C., and preferably, from about xe2x88x925.0 to about 70.0xc2x0 C., and most preferably, from about 0.0 to about 45xc2x0 C., including all ranges subsumed therein.
It is also noted herein that optional additives may be employed when cleaning with the surfactants described in this invention. Such optional additives include an oxidizing agent, like hydrogen peroxide, and an organic bleach activator such as those represented by the formula: 
wherein n is an integer from about 0 to about 20 and X is hydrogen or SO3M and M is hydrogen, an alkaline metal or an immodium cation. A more detailed description of such additives may be found in U.S. Pat. No. 5,431,843, the disclosure of which is incorporated herein by reference.
Other optional additives that may be employed to clean with the surfactants described in this invention include anti-static agents and deodorizing agents. Such anti-static agents typically include C8-C12 alcohol ethoxylates, C8-C12 alkaline glycols and glycol esters. The deodorizing agent, on the other hand, typically includes fragrances such as those described in U.S. Pat. No. 5,784,905, the disclosure of which is incorporated herein by reference.
Still other optional additives include viscosity modifiers like propylene glycol and sodium xylene sulphonate. As to the amount of optional additives used with the surfactants of the present invention, such an amount is limited only to the extent that the additive does not interfere with the cleaning process.